The present invention generally relates to automotive vehicle suspension systems, and pertains more particularly, to an automotive suspension system that is responsive to the vehicle steering to counter inertial forces on the vehicle chassis when in a turn to counteract and limit vehicle body roll.
Automotive vehicles have a body or chassis with an enclosed operator and passenger compartment with the body being resiliently supported by a suspension system on wheel assemblies that carry it over generally horizontal road and street surfaces. The vehicle may be driven by a drive train from the engine through the rear wheels, the front wheels or both. It typically has steerable front wheels and non-steerable rear wheels. The vehicle suspension system normally employs springs to support the body on the wheel assemblies, and with damping means in the form of hydraulic cylinders that act to dampen oscillations and movements of the body relative to the wheel assemblies.
The construction of the suspension system is often a compromise between a soft suspension for providing a soft comfortable ride for passengers over rough roads and a stiff suspension, which enhances the safety and stability of the vehicle, but is often uncomfortable for passengers. A stiffer suspension transfers more shock of the suspension to the chassis and offers less comfort to passengers but increases the stability of the vehicle. When the typical vehicle enters a turn the resulting centrifugal forces acting on the vehicle tends to roll the vehicle body about its roll center relative to the underlying suspension system. This centrifugal force also tends to displace the body laterally, outwardly tending to cause the vehicle to pivot about the contact of its outer wheels with the road surface.
The construction of a vehicle body and the configuration of the vehicle suspension systems determine the location of the roll center. In a conventional vehicle, the roll center of the vehicle is typically below the center of mass or gravity of the vehicle. Centrifugal forces tending to roll the vehicle body act on a lever arm or through a lever arm determined by the vertical distance between the center of gravity and the roll center. This is known as the roll couple.
Many of today""s vehicles, particularly cars and minivans are designed with a taller body to maximize interior space. Other vehicles such as sports utility vehicles (SUV) are built higher on the suspension for ground clearance. These configurations exaggerated in the roll couple, particularly when the vehicle is loaded. When these vehicles are empty, the center of mass is typically lower than when loaded. As more occupants are seated in the vehicle the center of mass moves higher above the roll center. This reduces the stability of the vehicle, making it relatively unsafe when entering a turn at moderate to high speed.
As a vehicle moves through a turn the body tends to roll toward the outside of the turn and shift the weight onto the outer wheels and springs while simultaneously unloading the inner suspension springs thereby reducing the cornering traction of the vehicle. The body also tilts or rolls toward the outside of the curve shifting the center of mass of the vehicle toward the outside of the curve.
Rolling of the body about its roll center when negotiating a turn is discomforting to the operator and to the passengers. A stiffer suspension will tend to reduce this tendency to roll but, will also subject the passengers and operator to the jolting and jarring of rough roads. A number of approaches to overcoming this tendency of the vehicle to roll during cornering have been proposed in the past. One approach, in addition to a stiffer suspension, has been to provide the vehicle with anti-sway bars in the form of torsion bars between the two sides of the suspension. This approach helps reduce roll to some extent but has not been entirely satisfactory
Another approach has been to provide the vehicle with linkage system powered by electric motors to selectively tilt the body of chassis and the wheels inwardly toward the inside of the curve during cornering. Several variations of such system are disclosed in U.S. Pat. Nos. 2,152,938; 4,632,413; 4,546,997; 4,650,213; and 4,685,690. These systems are complicated and expensive.
Other attempts at solving the cornering problems have provided for the wheels of the vehicle to tilt into a curve. These have been powered by various means such as electrical and hydraulic systems. One such system for tilting of the wheels that is powered or controlled by the steering of the vehicle is disclosed in U.S. Pat. No. 2,787,473. These systems are also complicated and expensive.
Others have attempted to overcome this problem by designing the suspension system so that the roll center of the vehicle is disposed above its center of its gravity. Most of these systems are also complicated and expensive. These systems also have other serious drawbacks. The inventor has provided suspension systems in co-pending patent applications wherein the suspension comprises an anti-roll linkage connected between the chassis and the moveable arm of the axles of the suspension system being responsive to a lateral force on the chassis to translate lateral force on the chassis to a vertical force on the down force side of the chassis so that the anti-roll linkage simultaneously applies a lifting force on the down force side (outside of the turn) of the vehicle and applies a lowering force on the up force side (inside of the turn)of the vehicle. However, these systems are not sufficiently simple and inexpensive for the average lower priced automobile.
Accordingly there is a need for an improved simple and inexpensive anti-roll suspension system that overcomes the above problems of the prior art for inexpensive automobiles.
The present invention solves the problem of excessive vehicle body roll. Broadly, the present invention provides a suspension system having a linkage that translates lateral body movement into a lift force on the down load side of the body.
More specifically, one embodiment of the invention comprises an anti-roll suspension for a vehicle chassis having at least two laterally spaced wheels, wherein the suspension comprises an axle assembly for rotatably mounting each of a pair of laterally spaced wheels, a spring assembly supporting the chassis on each of the axle assemblies, and an anti-roll linkage connected between vehicle steering system and the moveable arm of the axles of the suspension system being responsive to steering to translate steering of the vehicle to impose a vertical down force on the down force side (outside of turn) of the suspension so that the anti-roll linkage simultaneously loads the spring on the down force side of the vehicle and unloads the spring on the up force side (inside of turn) of the vehicle. However, the claims alone, not the preceding summary, define the invention.